_Red River_ rises about one hundred miles north-east of Santa Fé, in Mexico, at the base of a range of the Rocky Mountains, called the Caous, and after a very serpentine course of about two thousand five hundred miles, enters the Mississippi in thirty-one degrees fifteen minutes north latitude. There are many streams rising in the same mountains, flowing separately for three or four hundred miles, and then uniting to form the Red river. Of the regions in which the upper waters of these streams lie, but little is known. They are principally inhabited by the Pawnees. When the river enters Louisiana, its south bank is for a long distance the boundary between the United States and Texas. A great part of its course is through delightful prairies of a rich red soil, covered with grass and vines which bear delicious grapes. About a hundred miles above Natchitoches commences what is called the _Raft_; a swampy expansion of the alluvion to the width of twenty or thirty miles. The river divides into a great number of channels, many of them shallow; and for ages these channels have been becoming clogged with a mass of fallen timber carried down from the upper parts of the river. At this place its navigation is effectually obstructed, except in a high stage of water, when keel-boats of ten or fifteen tons burden may pass it through devious channels, or bayoux, and ascend several miles above. That part of the river situated above the Raft is rendered impassable for boats of burden, by shoals and sand-bars in a moderate stage of water.[9] The _Washita_, tributary to Red river, is navigable many miles. That portion of it situated within the valley of the Mississippi, denominated Black river, admits of constant navigation for boats of burden. White river is navigable in a moderate stage of water between three and four hundred miles. Of the rivers tributary to the Missouri, it is remarkable, that their mouths are generally blocked up with mud, after the subsiding of the summer freshet of that river, which usually takes place in the month of July. The freshets of the more southerly tributaries are discharged early in the season, and wash from their mouths the sand and mud previously deposited therein, leaving them free from obstructions. These freshets having subsided, the more northerly branches discharge their floods, formed by the melting of the snow, at a later period. The Missouri being thus swollen, the mud of its waters is driven up the mouth of its tributaries. These streams having no more freshets to expel it, their mouths remain thus obstructed till the ensuing spring.[10]